Continuous heating furnace and method of operating the same



Sept. 14, 1943. w. A. MoRToN 2,329,211

CONTINUOUS HEATING FURNACE AND METHOD 0E OPERATING THE SAME Filed May31, 1940 4 Sheets-Sheet l il J7 34.22

, BY f LZORNELYC( I Sept. 14, 1943. w. A. M-oRroN 2,329,211

CONTINUOUS HEATING FURNACE AND METHOD OF OPERATING THEYSAME Filed May31, 1940 4 sheets-sheet 2 w ATTORNEY Sept. 1 4, 1943. w. A MoRToN2,329,211

CONTINUOUS HEATING FURNACE AND METHOD OF OPERATING THE SAME Filed May31, 1940 4 Sheets-Sheet 3 f fffff 57 ATTORNEY Sept 14, 1943- 'I w. A.MoR'roN 2,329,211

CONTIYNUOUS HEATING FURNACE AND METHOD` OF 'OPERATING THE SAME Filed May51, 1940 4 sheets-sheet 4 f5" .7 Q 34 I i j Qa Z5 .55

t i ATTORNEY Patented Sept. A14, 1943 CONTINUOUS HEATING FURNACE ANDMETHOD OF OPERATING THE SAME William A. Morton, Mount Lebanon Township,

Allegheny County, Pa., assignor'to The Amsler- .Morton Company,Pittsburgh, Pa., a corporation of Pennsylvania Application May 31, 1940,Serial No. 337,987

49 Claims.

` This invention relates generally to heating furnaces and moreparticularly to heating furnaces of the type wherein articles are heatedas they are continuously moved therethrough, and the method of operatingthe same.

In the steel industry a continuous type heating furnace is employed forheating billets, ingots.,

blooms,4 slabs, rails and the like, to a predetermined temperature,preparatory tO rolling or per- I forming lother operations thereon.

This type of furnace may be made up 'of two chambers, namely a heatingchamber and the extension or preheating chamber.

The furnace chamber generally extends to the charging end of the furnacefor the waste gases which preheat the steel. 'I'hs preheatingoperationis a direct function of the rate of ring in the main heatingchamber and it is not independent thereof and can therefore not becontrolled'r The material to be heated continuously passes from thecharging end of the furnace, then through the preheating chamber, thenthrough the heating chamber, and 4across the soaking chamber, by whichtime it is uniformly heated and discharged from the other en d of thefurnace.

It has been customary to fire this character of furnace by directradiation from the flames adjacent the articles at one or more positionsthroughout the furnace, but it is impractical, to control the atmospherewith this method of firing. High-carbon and alloy steels are principallyaffected and decarburization takes place.

Variationsl in furnace temperature and undesirable furnace atmosphereconditions tend to break the original scale of oxidation from vthesurface of the material and an undesirable tight thin secondary scaleforms thereon. Conditions'of this character in heating create surfacedefects in the steel when Worked. Again heating by direct radiationfromflames adjacent the 'steel produces streaked heating in the steelWhich'is detrimental when rolling.

1n one direct radiation type heating furnace the flames are producedfrom burners adjacent.

the discharge end (Patents. 1,789,966; 1,912,933,

and 1,944,729) and flow over thesteel inthe opposite direction of itstravel for, the full length of the furnace. The hottest portion of theflames are adjacent the soaking hearth and the cool' gases aredischarged adjacent the steel charging to vary the rate ofproduction-and maintain the desired critical final steel temperature.This ob.-

viously creates thetendency of over-heating the steel. This isespecially'true if there is any interruption or change of the speed oftravel of the steel moving through the furnace. The rate "of heatexchange at the charging end of the fur'- nace is low and isdependent-upon the fixed or permissible rate of firing the heatingchamber.

In view of the fact that the hottest ame is ad' jacent the dischargeendit is impossible to employ more than of the available preheated air fromthe high temperature waste heat gases and thus the furnace operation isineiiici'ent. Each of these factors interferes with the heating of thesteel and especially high carbon and alloy steels. y

When the burners delivering a direct radiation type heating flame areplaced adjacent both -the discharging and the charging end .of thefurnace (Patents 1,476,142; 2,133,673, and 2,157,221) and the wastegases are roved adjacent the center of the furnace chamber, theefliciency is increased somewhat by reason of the fact that there is agreater heat exchange at the charging end than in the type of furnacereferred to above. However it is impossible to control the furnace at-.mosphere in the preferred manner. The' discharge end of this type offurnace is heated by and break away and produce an undesirable con-`direct radiation, making it difficult to control and equalize thetemperature across the steel when it is discharged, resulting in localoverheating and producing some of the difliculties asdescribed above. f

In both of these methods of heating by a direct radiating llame, coldair is drawn i-nto the furnace at the discharge end. Thisair chills thesteel causing the heavy original scale to contract A third type offurnace, which employs a direct l the furnaceatmosphereor to separatelycontrol end. With this type of furnace' it, is dilcult to maintain thedesired temperature of the steel be fore itis discharged and alsovirtually impossible the critical temperature of the steel whendischarged. i The burner'of `another type of furnace is posi- -tioned sothat the flame' directly im'pinges the steel at an angle and is divided,the smaller porvtion traveling with the steel across the soaking hearthand the larger portion traveling'against the movement of the steel tothe charging end. (Patent 2,056,904.) Since the gases are withdrawn fromthe furnace at both ends, the atmosphere ofthe furnace may be controlledt some degree. However the directI impingement of the fiame on the steellimits the ring temperature and streaked heatingl is pronounced. All ofthe other disadvantages mentioned above are also present to a degree.

The principal object of this invention is the vprovision of an improvedcharacter of furnace and the method of operating the same to overcomethese objectionable features and characfteristics.

Another object is the provision of a method for uniformly 'beating thesteel by diffused radiation ring.

Another object is the provision for local regulation of the temperatureof the steel on the soaking hearth independently of the principal firingof the heating chamber. This method of operation maintains the steel onthe soaking hearth at its -proper rolling temperature while the fuelsupplied to the heating chamber is varied or .completely shut off. Thisis exceptionally advantageous during periods in which the mill is shutdown' temporarily for repairs or changes of mill rolls.-

Another object 'is the provision for automatically controllingthetemperature of the steel as it is discharged regardless of the rateof production, or the rate of firing of the heating chamber, or duringmill delays.

Another object is to provide for an automatic control system whichregulates the temperature and furnace atmosphere conditions duringnormal operation, and during mill delays or reduced rates of productionautomatically stops the ring of the principal burners for the heatingchamber and transfers the fuel to the auxiliary burners for holding thesteel on the soaking hearth at rolling temperature during such delays,at any selected rate of ring.

Another object is the provision of a method for controlling the rate ofheating of the steel g in the furnace in proportion to the rate ofproduction ,without endangering Ithe k thermal or physicalcharacteristics of the steel in the criti-.

cal heating range. l

Another object is to provide a supplementary chamber for preheatingsensitive high carbon and alloy steels at a predetermined rate prior totheir entry into the main heating temperature. I

Another object is to pass the steel through a furnace in which theatmosphere adjacent the steel is a non-oxidizing atmosphere, differingfrom the normal uncombined combustibles.

Another object is the provision for an improved character of ring llamewhich enables control of the furnace atmosphere and the use of a higherthan normal percentage of -the waste heat recovery and which alsoenables one to vary the position of the maximum thermal input within thefurnace.

Another object is to combine the ow of all the gases of combustion asthey pass over the steel on the soaking hearth to obtain a diffusion ofthe total heat of the names, to thereby equalivze the temperature alongthe steel.

VAnother object is the provision for introducing and withdrawing theheating medium at the same end of the furnace.

Another object is the provision for introducing i and withdrawing theheating medium at both ends of the furnace.

Another object is the provision of means for controlling the percentageof inp ut and withdrawal of the heating'medium adjacent each end of thefurnace.

Other objects and advantages appear in the of a furnace red with threeames, two of which are redirected.

Fig. 3 is a sectional view taken longitudinally of a furnace fired withthree principal flames,

whereingonly the soaking chamber flame is re directed and twoindependent ames are provided for preheating. l

Fig. 4 is a sectional view taken longitudinally of a furnacefired withtwo flames, the flame supplying heat to the soaking chamber beingredirected.

Fig. 5-is a sectional view taken longitudinally of the furnace having asloping hearth and fired with opposed redirected flames, the mainfurnace chamber ilame normally supplying approximately of the heatdelivered to the furnace.

Fig. 6 is a sectional view of a furnace having' a sloping hearth similarto that shown in Fig. 5 and which is provided with a preheating chamber.

Fig. 'I is a diagrammatic view illustrating the circuits forautomatically controlling the temperature of the air and fuel deliveredto a furnace such as that illustrated in the previous iigures, and thefurnace pressure control for the same. The outline of the furnace usedto illustratezthese controls is taken on the line 1 1 of Fig.

Fig. 8 is a graph illustrating the temperature characteristics of thefurnace disclosed herein which includes the preheated air delivered tothe furnace, the furnace temperature, and the temperature of the steelas it passes therethrough.

Referring to Fig.. 1, the furnace illustrated therein comprises threeprincipal elements. the main heating chamber III, the soaking hearth IIin one end of the main heating chamber, and the preheating chamber I2,Water cooled skids I3 extend through the preheating and heating chambersfor supporting the material Il to be heated which is charged through theopening I5 and is shoved in the usual manner, through the preheatingchamber, the heating chamber and over the soaking hearth, from whence itis discharged through the opening I6. The soaking .hearth Il is a solidhearth. The openings I5 and I6 are closed with suitable doors.

The main heating chamber I0 is divided by the steel charge Il into upperand lower independent chambers II and I8. The chamber I1 above the steelis formed by the enclosing roof structure I9. The height of thesechambers may be determined by the formula governing the expansion ofgases from 60 F. to 2500* F. with the assumption that the averagefurnace temperature will reach the latter amount, and thus by employingthe proper firing rate, the furnace pressure is maintained constant.

The roof structure above the soaking hearth II may also be determined inthe same manner.

The preheating chamber Il is likewise divided by the `steel charge Ilinto the upper and lower independent chambers 20 and 2|. Each of thesechambers connect with the independent chainbers I1 and I8 of the mainheating chamber and thus form continuous upper and lower independentchambers in these two sections of the furnace.

The lower chamber I8 is below the plane of the hearth and is enclosed bythe sub-floor 22 and the continuous outside walls 23, which carry theouter skids I3, andwhich extend from the intermediate transverse wall 24adjacent the soaking hearth II to the charging end of the preheatingchamber I2 as indicated at 25.

The rear wall 26 ofy the furnace, through which the preheating chamberI2 opens, is provided with two rows of burners 21 and 28 for firing thechambers I1 and I8 respectively. The burners are supplied with fueltransmitted through the conduits 30 and with preheated air transmittedthrough the conduits 3I and 32. Burners are provided between the Walls23 and the side walls of the vfurnace as shown in Fig.'7. However aportion of the ames of these burners may pass upwardly over the ends ofthe steel to the chamber I1.

The soaking hearth II is locally heated as desired bya flame issuingfrom the row of burners 33 in the front Wall 34 of the furnace. Ordi-vnarily these burners are operated onlyduring mill delays, during whichtime the preheated air and fuel -are transferred from the burners 21 and28 to the burners 33 which are described below in relation with thefurnace control and operation.

It will be noted that each vof the burners 21,

steel on the soaking hearth II and is discharged at the front of thefurnace. 'Ihe paths of the gases are indicated in each of theA views bydotted lines.

Flues 35 are positioned just inside the charging opening I5 fordrawingoff the main portion 28 and 33 are substantially horizontally disposedand that they are spaced further from the plane of the hearth than theyare from the rcof or the floor. The reason for this arrangement is toprovide a flame that travels outwardly in a path substantially 'parallelwith the steel until its velocity is reduced to such an extent that thedraft, which is induced in the vicinity of each burner, redirects thepath. of movement of the products of combustion. Combustion issubstantially complete in each flame before it is redirected by thedraft forces and the hottest part of the flame does not impinge directlyon the steel. Thus the products of combustion of each ame blanket thesteel on its return path of movement to the ues. In this manner theatmosphere surrounding the steel may be controlled to prevent localoverheating, excess oxidation and decarburization f the steel.

The hottest portion of the llame is along the. initial path ofprojection. Thus the .steel is heated by radiation from this portion ofthe ame and by convection from the products of combustion passing backover the steel. The radiant heat energy reflected` from the roof anddirectly effective from the flame must pass through the products ofcombustion owing back over the steel. The radiant heat energy is thusdiffused as it passes through the products of combustion, therebyuniformly heating the steel laterally across the furnace, and thedetrimental effects of direct heating from initial flame combustion areeliminated. Again the eiliciency of the heat exchange is increased bythe extension of the flame length and the location of the area of thehighest rate of heating may be accurately controlled.

This method of heating utilizes direct radiation and in addition directconvection in combination to accelerate the normal heating rate of theproducts of combustion fromV the upper chambers I1 and all of theproducts of combustion from the lower chamber I8. These waste gases areselectively drawn through the independent upper and lower lchambers 20and 2I of the preheating chamber I2 in their travel to the flues 35 andthus regulably preheat the steel to any desired temperature for deliveryinto the heating chamber. If this chamber were not added at the rear ofthe furnace the gases would pass directly from the chambers I1 and I8 tothe vertical flues 35 which direct them through the horizontal flue 36,the recuperator 31 or other heat absorbing device, to themain flue 38,from whence they are ordinarily directed to a stack. If desired thegases may be carrled'directly to the stack and the airpreheater'omitted.

I'hat portion of the products of combustion from the burner 21 whichflows over the steel on the soaking hearth II is drawn down past thesteel discharge opening I6 into the flues 39 where they may bedischarged directly to the short. damper controlled auxiliary stack 40.

During mill delays when the firing is instantaneously switched from theburners 21 and 28 at the rear of the furnace to the burners 33 at thefront of the furnace the flames project over the soaking hearth and whentheir velocity is diminished the products of combustion are redirectedback over the steel, as described above, and are discharged down pastthe steel discharge opening VI6 through the flues 39 to the stack 40 asdescribed above.

The flues 35 and 39, 'which direct the gases from the plane of thehearth, may in each case be a single flue or may comprise a plurality ofsmaller flues, depending upon the character of the furnace structure. Inthe latter case they usually open into a single connecting flue 36 attheir lower ends.

The flues or outlets are thus positioned in the vicinity of the burnersand the gases discharged from the furnace chambers pass both thecharging and discharging openings I5 and I6, thus carrying away any coldair that may lter into the furnace and preventing its access to the hotsteel on the hearth even when the doors are open.l

The steel is thus protected from cold air and is blanketed by theproducts of combustion. This avoids surface temperature variations whichwould tend to break the original scale of oxidation from the surface ofthe steel and'thereby avoids the formation of the thin tight secondaryscale which is highly objectionable. 'I'he removal of the heavy scaledeposited on the hearth, which would necessitate shutting down thefurnace is also avoided.

This character cf flame provides uniform heating of the steel andpermits accurate control of the heating cycle.

The flue 35 may be controlled by the damper 4I which in turn may beoperated by the servomotor 42. The flue 39 is likewise controlled by thedamper 43 operated by the servomotor 44. The main' flue 38 which leadsto the stack is controlled by thedamper 45 operated by the servornotor48.

The rate of preheating the steel may be controlled by damper 4| toregulate the quantity of waste heat leaving the charging end of thefurnace. y

A pyrometer 41 is placed in the flue 39 for registering the temperatureof the gases flowing off the steel in the soaking hearth.

In Fig. 2 a greater portion of the gases passing from the lowerindependent heating chamber I8 are carried off by the flue 48 in thecenter of the furnace, which is controlledby the damper 50 operated bythe servomotor I, to the horizontal flue 36. The balance of the productsof combustion of the flame issuing from the burner 28 passes back alongthe steel through the lower preheating chamber 2| and is discharged outthe flues 35, thus forming a thinner layer of waste gas which preventsthe flames from coming directly in contact with the steel.

The preheating chamber I2 in Fig. 2 is much .the same as in Fig. 1.

The flues 39 carrying the gases over the soaking hearth Il are connectedwith the horizontal flue 38. In order to prevent uncontrolled migrationof lthe gases, -which might upset the firing conditions therein, thedampers may be regulated to produce a draft of .04 inch of water in theflues 35 and 48 and a draft of .06 inch of water in the flue 39.

In Fig. 3 the independent chambers 20 and 2I of the preheating chamberI2 are fired directly by the upper and lower rows of burners 52 and 53,respectively, which control the rate at which it is desired to preheatthe steel prior to delivery in the mainv heating chamber. The productsof combustion from the llames of these burners pass into the mainheating chambers I1 and I8, because combustion is substantially completewhen these flames pass into the main heating chambers and their productsof combustion blanket the steel from initial flames of combustion inchambers I1 and I8 to produce substantially the same effect as thatobtainable with the structure illustrated in Fig. l,

The hottest part of the flames issuing from the main burners 21 and 28is thus prevented from heating the steel by direct radiation. Thepreheated steel is thus subjected to diffused radiant heat energy fromthe furnace surfaces and the llames in both the upper and lowerchambers. When combustion of the arnes from the burners 21 and 28 lssubstantially complete the products of combustion from both thepreheating burners and the main burners combine and equalize intemperature as they continue to` blanket the steel with an inertatmosphere of uniform temperature until it is discharged.

In the case of the structure illustrated ln Fig.'

3 any cold air that may filter into the furnace through the chargingopening I5 aids in supporting the combustion of the preheating flamesand the free oxygen ls substantially all consumed before the gases passout of the preheating chamber. Thus the infiltration of the cold airdoes not have an opportunity to injure the heated steel which is not ata critical temperature adjacent the point of entry andsuch air is usablein this design of furnace.

The hot gases of combustion from the lower preheating chamber 2I form aprotective layer between the steel and flames from the burners 28 in thechamber I8. The products of combustion of the flames issuing from theburners 28 mix with the products of combustion from the preheatingchamber 2l and pass down nues 48 out of the chamber I8. Gases from thechamber I1 travel along, blanketing the steel over the soaking hearthand finally pass down outlets 39. All flues or outlets are provided withindependent damper control as described above and are further subject tocommon damper regulation by furnace pressure control.

The heat delivered to the soaking hearth from the redirected flames ofthe burners 33 is preferablyA applied only during mill delay orinterruption of normal operation. .At the time of interruption the heatwill be automatically turned on by means of the control system which isherein described. The burners 33 may or may not be used at any time,depending upon the changing conditions within the furnace, but theseburners are always subject to independent automatic control whendesired.

As previously described the flames from the .burners 33 must passthrough the previously produced blanketing gases to the steel and as theforward velocity of thev flame diminishes the llame is returned by draftin the flue 39 and the gases therefrom mingle with the other products ofcombustion and travel down past the discharge opening I6 through theflue 39, the horizontal flue 36, to the recuperator.

The furnace illustrated in Fig 4 is not provided with a preheatingchamber I2 nor a lower heating chamber I8. However the burners 21 and 33function in the same manner as that just described in'connection withFig. 3. This view illustrates some of the details of an actual furnacestructure of the charging and fired type, whereas the previous views arerelatively diagrammatic. K

A portion of the gases flowing through the horizontal flue 36 are drawnup the passageway 49 through the floor 22 and pass over the ends of thesteel into chamber I0 to form a blanketing protection through which theradiant heat from the ame issuing from the burners 21 must pass to heatthe steel. These gases are drawn off at the rear of the furnace throughthe flues 35 which in this instance pass directly to the stack 38. Thusthe same effect is produced in this furnace as that described inrelation to the previous furnaces.

In Figs. 5 and 6 a sloping hearth is provided for receiving.cylindrically shaped articles I4 wich are to be heated. These articlesare charged through the rear opening I5 and are progressively rolleddown the hearth manually. Entrance to the furnace chamber is gainedthrough the doors along the side walls. The

steel ls discharged laterally through the openthe radiant heat of2,329,211 steel and is discharged through the flues 35 while theremaining portion ows over the soaking hearth Il and out the ues 39 tothe auxiliary stack 40. The roof I9 being substantially horizontal iseconomical to construct and becauseof the sloping hearth the heatingchamber l progressively increases in volume towards the front of thefurnace. The roof over the lower end of the hearth Il is also horizontaland the connecting roof, which slopes from one roof level to the other,restricts the inner end of the heating chamber I0. The slope of theconnecting roof thus aids in redirecting the flame from the burner 21 bythe restriction. The blanketing gases traveling back up over the steelare discharged downwardly through the flue 35 tol the recuperator 31.

The slope of the hearth enlarges the volume of the chamber over thesoaking hearth Il toward the front of the furnace, thus aiding inredirecting the flame from the burner 33 during mill delays, and causingthe burned gases to travel down over the steel on the hearth and thusblanket it from direct radiation. These gases are 'discharged throughthe flue 39 to the auxiliary stack 49.

The quantity of gas passed out the stack 40, during normal operationswhen the burners 33 are shut down, will .be merely suicient to providea. measure of the final heated temperature of the steel prior to`discharge Whichhas not been pro-` nace shown in Fig. 6 is desired toprovide the largest chamber for approximately 60% of the V)furnacelength at the front of the furnace and the smallest chamber forapproximately 40% of the furnace *for the smallest chamber which in thisinstance is the preheating chamber I2.` In each instance the recuperator31 is connected to vided for in this manner for this or any other theoutlets of the chamber containing the largest ring proportion, which. inFig. 6 is the preheating chamber l2 and is connected through the flue 39to the recuperator in the same manner a that described in relation toFigs. 1 and 2.

In both of these structures the steel is protected by the blanketingvlayer of products of combustion and any infiltration of cold air at thecharging or discharging openings is carried along with Waste heat gasesand cannot produce any detrimental effect on the steel.

Fig. '7 is a diagrammatic view showing the automatic control circuitsfor operating anyone of the above described furnaces. lined is shown asa plan view of the hearth shown in the furnace of Fig. 2 which isrepresentative of each of the furnace structures comprising thisinvention. Independent preheating burners 52 and 53 are employed only inthe furnace shown in Fig 3. These preheating burnersfor all practicalpurposes may be fed by branch lines from the main burners and thereforemay be considered auxiliary to the main burners 21 and/.28 insofar asthe controls are concerned. It may or may not be desirable to providethe preheating burners with preheated air and to avoid perplexity Vtheyare not illustrated in Fig. '7.

60 represents the blower for delivering air to the recuperator 31 whereit is preheated and di- The furnace outrected to the burners 21 and 28or to the burners 33. A Venturi tube 6|` is inserted in the blower inletwhich is controlled by the damper 62 operated by the servo motor 63.

`The fuel is supplied through the conduit 64 and its flo'w is controlledby the regulating valve 6,5 which is operated by the motor 66. When thefuel passes from the valve 65 it must flow through an orice plate 61 andthen continuesthrough the supply conduit to the burners 21 and 28 or tothe burners 33. Each of these sets of burners is provided with ahand-operated valveli for independently adjusting the flow of fuel toeach of the burners. The ow of fuel .may be read by the meter 69.

The burners are preferably of the induction type and the preheated airin the common ducts while it is induced it is also proportioned by theorifice 61'in the fuel line to the other diaphragm of the air-fuelregulator and register the quantity of fuel delivered to the furnace.The quantities of air and fuel are thus kept proportional by means ofthis vratio regulator control which is operated by differentialpressures created by the flow of air and the quantity of fuel ismaintained proportional. The quantity of air is previously determined bythe temperature of the furnace.

The temperature of the gases being discharged from the furnace throughthe flue 39 has a direct relation to the temperature of the steel on thesoaking hearth which the gases have just passed over, Whether thesegases are coming from the main burners 21 during normal operation orfrom the burners 33 during mill delays. furnace temperature isapproximately 2500 F.

.the steel on the soaking hearth will be approximately 200 F. less. Thisdifference may vary slightly but for purpose of control the waste gasesalways bear a direct relation'to the steel temperature whereby thefurnace control system may be accurately operated. Y

The temperature ofthe gases discharged from the furnace is measured bythe pyrometer 41 and registered in the recording potentiometertemperature control 13. This control in turn operates the servo motor 63for opening and closing the damper 62 and thereby regulates the amountof air delivered to the furnace for controlling the temperature.

Any change in the quantity of air delivered to the recuperator isregistered as differential pressures in the air-fuel regulator 1I whichactuates the ratio control 14 for automatically main- '.taining apredetermined ratio of air and fuel When the In order to maintain thefurnace at a predetermined pressure an atmosphere connection in thefurnace is made through the conduit 16 to the pressure regulator 11 forcarrying pressure impulses thereto. These impulses are relayed throughthe furnace pressure control device which opens a high pressure valve inlines 18 to open ports in the opposite ends of the fluid operator motor46 for regulating the main damper 45 in the flue 38 leading to thestack. The furnace pressure regulation is supplemented by al sible andpractical for the first time in continuous furnace practice.

During normal mill operation the potentiometer temperature control 13 ofthe furnace control regulates the flow of air delivered to the fur- -vnace and the regulator 1I proportions th'e flow of fuel with thequantity of air being delivered to the furnace. The air and fuel linesare each provided with the Y connections 8D and 8|, respectively, forconducting the air and fuel to one of two branch lines. One branch lineconnects with the main burners 21 and 28, and the pre- Vheating burners,if any, for normal operation of Th'e other branch line connects thefurnace.' with the burners 33 for operation delays.

Each of these branch lines is controlled by a solenoid operated valvewhich preferably has a spring return action for closing the valve. Thisarrangement provides a safety feature in case of a power failure. Thevalves 82 and 83, in air and fuel branch lines respectively, control thelines leading to the main burners at the rear of th'e furnace and areelectrically energized through the common return wire 84 and the controlwire 85. The valves 86 and 81, in the air and fuel branch linesrespectively, control the lines leading to the mill delay burners at thefront of the' furnace and are electrically energized through the commonreturn wire 84 and the control wire 88. These control wires areconnected with' the selection switch 90 which in turn is operated by theservo motor 63. The switch 90 is provided with electrical energy fromany suitable source such as indicated by the wires Si.

The switch 90 selectivelyenergizes either set of valves for controllingthe normal operating main burners 21 and 28 or the mill delay burners33. This selection is determined automatically by the temperature of thefurnace. The furnace controls are adjusted to provide the proper firingduring mill conditions for th'e desired rate of reduction.

With this adjustment normal operation of the furnace is automaticallycontinued by moving the steel therethrough at the chosen predeterminedrate of speed. If hot steel is `not taken from the furnace at the normalrate, by feeding cold steel thereto, the furnace temperature willquickly rise. This rise in temperature isiimmediately registered by thepyrometers 41 in the potentiometer temperature control 13 whichenergizes thel servo motor 63 to reduce the quantity of air delivered tothe furnace. The reduction of air thus automatically reduces thequantity of fuel through the regulator 1l and the air fuel ratio control14. As the quantity of heat energy delivered to'the furnace is reduced,the furnace temperature falls to normal.

If no steel is taken from the furnace the temperature rises very fastand initiates the automatic operation just described. When thepotentiometer control 13 reduces the quantity of air delivered tothefurnace to a predetermined amount, such Aas 50%, then the servo motor63 throws the switch -90, thereby selectively changing the firing fromnormal operation at the rear of the furnace to the mill delay burners 33at the front of the furnace by deenergizing and closing the air and fuelvalves 82 and 83 and energizing and opening the air and fuel valves 86and 81.

The waste gases from the redirected ames of the mill delay burners 33continue to control the temperature of the steel on the soaking hearthil and the automatic controls continue to function in the same manner.The fuel consumption during mill delays is naturally materially lessthan that required for normal furnace operation because the small amountof steel on the soaking hearth is all that is maintained at rollingtemperature. Again this steel is not o verh'eated and is always readyfor use.

When mill operations are resumed, hot steel is discharged from thesoaking hearth and cold steel is charged into the rear of the furnace,the gases discharged through the ues 39 become cooler because thefurnace temperature drops due to increased absorption o'f heat by thecooler steel moved onto the soaking hearth and. into 'the furnace. Thepyrometer 41 then actuates lthe potentiometer temperature control 13which in turn energizes the ser'vo motor 63 for operating the damper 62to increase the quantity of 'air delivered to the furnace. The air-fuelratio regulator 1l and the control 14 are operated by the change in thequantity of air delivered to increase the quantity of fuel delivered tothe furnace. When the quantity of air delivered to the furnace reaches apredetermined amount the servo motor 63 actuates the selectionsswitch 90which deenergizes the valves 86 and 81, causing them to close andenergize the valves 82 and 83, causing them to open and thereby transferthe firing from the front to the rear of the furnace. Thus the furnacehas been restored to normal 'operation' for continued mill production.

The selection switch 90, which controls the transfer of firing fromnormal operation to mill delay operation, maybe designed to operate thetransfer valves in the branch lines when 50% ofv the normal amount ofair is delivered to the furnace as stated above. being made from milldelay operation to normal operation of the furnace this selection switch90 maybe made to operate when the quantity of air delivered to thefurnace reaches 40%, 50% or 60% as desired. This adjustment isadvantageous in the control system as different fuels and differentcharacters of furnaces may require faster or slower pick up to aeturnthem to normal operation.

When the transfer is Again the transfer valvesy 82, 83, 8B and 81 may bearranged to proportion the quantity of air and fuel between the rear andfront of the furnace, in which case the burners 21, 28 and 33 Will allbe firing at the same time and a greater differential will be providedbetween the complete transfer of the firing from one end of the furnaceto the other.

This automatic control system may be applied to furnaces of this typeother than that disclosed herein. However it is particularlyadvantageous for use with these furnace structures.

If it be necessary to turn off the burners in the preheating and mainheating chambers because the mill is shut down for roll change orrepairs, the steel on the soaking hearth may thus be kept at rollingtemperature automatically by means of this control system whichmechanically transfers the firing operation froml the main burners tothe mill delay burners 33. When the mill is again ready for hot steelthe furnace is prepared todeliver it immediately from the soaking hearthand the burners in the main furnace and the preheating chamberautomatically resume operation inlmresponse to initiation of cold steelcharging creating a Vfuel demand. This represents ay material advance inthe continuous furnace art.

The graph illustrated in Fig. 8 shows the temperature conditionsthroughoutthe continuous furnaces disclosed above. The upper curve FIrepresents the temperature of the furnace throughout its length when itis being used for low carbon steel. F2 represents the temperature of thefurnace when heating alloy or high carbon steels. The respectivetemperature of the low carbon and high carbon steels as they passthrough the furnace under these conditions is represented by the curvesSI and S2. Obviously more low carbon steel may be heated, but highcarbon steel may be heated under the particular conditions or safecontrolled rates of temperature acceleration in the same furnace safelyfor the first time.

' The temperature of an ordinary continuous type of furnace such as thatfound in the prior art is illustrated as curve F3 in Fig. 8. In suchcontinuous type furnaces the temperature within `the main heatingchamber is highest between the center of the chamber and a soakingchamber, whereas in this improved furnace with above disclosed method offiring the same, the highest temperature is vadjacent the charging endof the main heating chamber and the temperature gradually diminishes tothe discharge end of the furnace, thereby providing a preferred state ofthermal equilibrium, in that the gases, steel` and `furnace parts aresubstantially uniform across the furnace. In ordinary continuous typefurnaces these temperature conditions are not attained. e

If the preheating chamber beeliminated these curves start at thecharging end of the heating chamber but they assume substantially thesame character as that illustrated. `If the preheating chamber and themain heating chamber are shut down because of the interruption of milloperations the furnace remains closed and the steel ceases to movetherethrough. The temperature of these chambers and the steel thereinslowly lowers while the temperature of the steel in the soaking chamberis maintained at the proper amount. After many hours under theseconditions there is a* uniform gradation in the steeltemperature fromthe inlet end of the soaking chamber to the charging door I5.

The supplementary preheating chamber may or may not be used. dependingupon the type of steel or rate of production desired. It is obvioushowever that when -a high rate of production is desired from low carbonsteels, the supplementary chamber may be operated at a very hightemperature, thereby increasing the temperature of the steel prior toits entry into the main heating chamber. In the case of special steelsrequiring a controlled preheating cycle, the rate of temperature rise inthe steel may be controlled independently of the rate of `firing in theheating zone. The prior art does not disclose furnaces which have thisfunction. In Patent No. 2,157,221, of which the present inventor t is aco-"patentee, the center outlet prevents the gases of the preliminaryburner from protecting the steel Iand also prevents regulation of thebottom heating chamber independently of the top chamber. I prefer to usea substantial portion of the heating cycle for preheating but generallythis will be less than half or the furnace investment will be improperlydistributed.

I claim: f

1. The method of heating billets and the like in a continuous furnacewhich comprises causing heating flames which produce radiant heat energy to travel from both ends of the furnace and toward each other inlines substantially parallel to the path of the billets, interposingbetween the billets and the heating iiames a blanketing layer ofnon-oxidizing gases through which the radiant heat energy passes to heatthe billets and withdrawing the non-oxidizing gases after they havepassed over the billets about to be discharged.

2. The method of heating billets and the like in a continuousfurnacewhich comprises causing heating flames to travel from both ends of thefur- .nace and toward each other in lines substantially tially parallelto the path of the billets, interposing between the billets and theheating names a blanketing layer of non-oxidizing products of Combustionoriginating from the heating flames and withdrawing the non-oxidizinggases after they have passed over the billets about to be discharged.

4. The method of heating billets and the like in a. continuous furnacewhich comprises causing heating flames to travel in lines substantiallyparallel to the path of the billets and above and below the same, andinterposing between the billets and the heating flames blanketing layersof vnon-oxidizing products of combustion originate ingfrom theheatingflames. l

5. The method 0f heating billets andthe like in a continuous furnacewhich comprises causing heating flames to travel from both ends of thefurnace and toward each other in lines substantially parallel to thepath ofthe billets and redirecting the non-oxidizing products ofcombustion of the flames from they/discharge end to for heating travelbetween the billets and the heating flames to provide a blanket heatenergy of the heating flames travels to heat the billets.

6. The method of heating billets and the like in a continuous furnacewhich comprises causing heating flames to travel in lines substantiallyparallel to the path of the billets and above and below the same andredirecting the non-oxidizing products of combustion from said flames totravel between the billets and the heating flames to provide blanketsabove and below the billets through which the radiant heat energy of theheating flames travels to heat the billets.

'7. The method of firing a continuous furnace billets and the like whichcomprises causing heating flames which produce radiant heat energy totravel in the direction of the travel of the billets in the furnace,dividing the non-oxidizing products heating flames and controlling thedivision of the products to cause a portion of the products to travelwith the billets and in contact therewith toward the discharge end ofthe furnace to blanket the same and redirecting another portion totravel in the reverse direction between the parent flames and thebillets to form a blanket through which the radiant heat of the flamespasses to heat the billets by regulating the withdrawal of the productsfrom both ends of the furnace.

8. The method of firing a continuous furnace for heating billets and thelike which comprises causing heating flames to travel above and belowthe billets in the direction of their travel in the furnace, dividingthe non-oxidizing products of combustion from the heating flames andcausing portions of the products to travel with the billets andredirecting other portions to travel in the reverse direction betweenthe parent flames of' the billets to form blankets above and below thebillets through which flames passes to heat the billets.

9. The methods of firing a continuous furnace for heating billets andthe like which comprises causing heating flames to travel with thebillets to preheat the same before their entry into the heating chamberof the furnace, causing other heating flames to travel with the billetsas they travel in the heating chamber while interposing thenon-oxidizing products of combustion of the preheating flames betweenthe second mentioned flames and the billets to provide a blanket throughwhich the radiant heat energy passes from the second mentioned flames toheat the billets.

10'. The method of firing a continuousV furnace for heating billets andthe like which comprises causing heating flames above and below the sameto preheat the billets `before their entry into the heating chamber ofthe furnace, causing other heating flames. to travel with the billetsboth above and below the same as they travel in the heating chamberwhile interposing the non-o products of combustion of the preheatingflames between the second mentioned flamesand the billets to provide ablanket through which the radiant heat energy passes from the secondmentioned flames to heat the billets.

1l. The method of firinga continuous furnace for heating billets and thelike which comprises causing heating flames to travel in the directionof the travel of the billets in the furnace, dividing the non-oxidizingproducts of combustion of combustion from the to travel with the billetsthrough which the radiant the radiant heat of the in contact with thefrom the heating flames and causing a portion of the products to travelwith the billetsand in contact therewith toward the discharge end of thefurnace and redirecting another portion to travel in the reversedirection between the parent flames and the billets to form a blanketthrough which the radiant heat of the flames passes to heat the billets,causing additional flames to travel in the opposite direction to theabove mentioned flames, and redirecting the nonoxidizing products ofcombustion of the last mentioned flames to travel with the billets toprovide a blanket through which the radiant heat energy of the lastmentioned flames pass 4to soak the billets.

l2. The method of firing a continuous furnace for heating billets andthe like which comprises causing heating flames to travel with thebillets to preheat the same before their entry into the heating chamberof the furnace, causing other heating flames to travel with `the billetsas they travel in the heating chamber while interposing thenon-oxidizing products of combustion of the preheating flames betweenthe second mentioned flames and the billets to provide a blanket throughwhich the radiant heat energy passes from the billets, causingadditional flames to travel in the opposite direction to the secondmentioned flames, and vredirecting the non-oxidizing products of.combustion of the last mentioned flames to travel with the billets toprovide a blanket through which the radiant heat energy of the lastmentioned flames pass to soak the billets.

13. The `method of controlling the operation of a continuous furnace forheating billets and theA like which comprises regulating the intensityof heat supplied to the furnace in response to variations in thetemperature of the discharged gases in the flue after they have flowedoff the heated billets at the discharge end of the furnace.

14. The method of controlling the operation of a continuous furnace forheating billets and the like, which comprises regulating the quantitiesof fuel and air supplied to the furnace in response to variations in thetemperature of the discharged gases in the flue after they have flowedoff the heated billets at the discharge end of the furnace.

l5. The method of controlling the operation of a continuous furnace forheating billets and the like, which comprises regulating the intensityof heat supplied to the furnace in response to variations in thetemperature of the products of combustion in the flue after'they havepassed heated billets at the discharge end of the furnace.

16'. The method of controlling the operation of 'a continuous furnacefor heating billets and the like by combined fuel and air whichcomprises regulating the supply of one of the heating elements inresponse to variations in the temperature of the products of combustionin the flue after they have passed in contact with the heated billets atthe discharge end of the furnace, and regulating the supply of the otherheating element in response to the supply of the first mentioned heatingelement.

17. The method of controlling the operation of a continuous furnace forheating billets and the like and which is arranged to be fired at bothends which comprises regulating the quantities of heat supplied toeither end in response to the temperature of the products of combustionin the iliue .after they have passed in contact with second mentionedflames to heat the ment- 'of the 'travel in the v while asaazaii the theheatedbillets at the discharge end of furnace.

18. The method of controlling the operation of a continuous furnace forheating billets and the like and which is arranged for firingadjacent'both ends which comprises during normal operation heating thebillets by tiring adjacent the charging end of the furnace, and, duringa temporary cessation of travel of the billetswithin the furnace,maintaining the heat of the billets adjacent the discharge end of thefurnace by ring adjacent the discharge end.

19. The method of controlling the operation a continuous furnace forheating billets and th like and which is' arranged for firing at bothends, which comprises during normal operation heating the billets byilring adjacent the charg- `nace having a preheating portion, a mainheat- A Aingl portion and a soaking hearth, which comprises causing'heating llames to travel in the direction ofy the movement ofthe-billets and above and xbelow the same to preheat the same as they-pass through the preheating portion. causing heating llames to travelwith the billets in the main heating portion and above and below thesame to heat the preheated billets, and

'saturating the heatedbillets with heat'from that portionof the productsof combustion ofthe Y heating flames above the billets while the billetsing end of the furnace.. and, during a temporary cessation of travel ofthe billets within the furnace, maintaining the heat of the billetsadjacent the discharge end of the furnace by firing ladjacent thedischarge end. and regulating the quantity of firing vin either instancein response tothe temperature of the products of combustion passed incontact with the heated billets adjacent the discharge end of thefurnace.

20. The method of controlling the operation of a continuous furnace forheating billets and.

the like and which is arranged for ring at either end. which comprisesduring normal operation heating the billets vby firing adjacent thecharging end of the furnace, and in case of a tempothe billets in themain heating portion to heat are passed over the soaking hearth.-

25. The method of heating .billets and the i like while passing themthrough a continuous furnace having a preheating portion, a main heatingportion and a soaking hearth, which com-- prises` causing heatingflamesto travel in the direction of the movement of the billets topreheat the same as they pass through the preheat-l ing portion, causingheating dames to travel with the preheated billets. saturating theheated` billets with heat from the products of combustion of thepreheating and heating flames while the vbillets are passed over the'Asoaking hearth, and regulating the temperature of the soaked billets Abythe temperature of' the saturating products rary cessation of travel ofthe'billets in the furnace as the furnace temperature tends to riseabove a predetermined degree-switchingthe iiring to the discharge end ofthe furnace, and upon resumption of travel of the billets again switch-.ing the firing to the charging end of the furnace. 2l. The methodofheating billets and the like hile passing them through a continuousfurnace-having a preheating portion and a main heating portion, whichcomprises causing heating ilamesto travel in the direction of themovement or the billets to preheat the billets1as they passthroughthepreheating portion, and causing heating names tol travel in the same'direction to heat the preheated billets as they'pass through the mainheating portion.

22. The method of heating billets .and the like whiley passing themthrough a continuous' furnace having 'heating portion,- which comprisescausing heata preheating portion and a main prises causing heatingflames to travel in the direction of the movement of the billets topreheat the same as they pass through the. preheating porti0`n,2ausingheatingA flames to travel with'A ,the billets in the main heatingportion to heat the preheated billets, and saturating the' heatedbillets with heat from the products of combustion of' the preheatingandv heating flames` while the billets arepassed over the soakix'ighearth.'

24. The method of heating billets and the like passing them throughacontinuous' furportion, a main heat-A ling. portionand a soakinghearth, which com- .0f combustion billets.

26. In a continuous furnace for heating bilu lets and the like andthrough which the billets are caused to pass from the charging end tothe discharge end, means vfor introducing heating llames at the chargingen'd of the'furnace which vtravel in the, same direction as the 'billetsfor preheating the same, and means for introducing additional heatingflames in-the same direction y as the preheating flames for heating thepreheated billets to an elevated temperature.

27. In a continuous furnace for heating billets and the like and.through which the billets are caused to pass from 'the charging end tothe discharge end, means for introducing heating llames above and belowthe billets at the' charging end of vthe furnace which travel in thesame direc- 'tion as' the. billets for preheating the same, and

means forintroducing additional heating flames above an'd below thebillets and in the same direction as the preheating llames for heatingthe preheated billets to an elevated temperature.v .28. In acontinuousfurnace for heating billets and the'like and through which thebillets are same direction above and. below liu caused to pass fromI thecharging end to the discharge end, means for introducing heating llamesat the charging end of the'furnace which travel in thesame direction asthe billets for preheating the same, means for introducingv additionalheating ames in the same direction' as the preheating ames for heatingthe preheated billets j' to an elevated temperature, a soakinghearthover which the billets travel before theyare discharged from thefurnace, andl means for withdrawing the products of combustion of saidllames over thebiilets on the soaking hearth fand discharging them fromthe furnace.

29. Ina continuous .furnace for heating billets andthe like and throughwhich the' billetsare caused to pass from the charging end to thedischarge' end, means 'forl introducing heating names above and belowthe billets at the charging end ofthe furnacewhich travelfin the samedirection as lthe billets fo'r preheating the same, means for iintroducing additional4 heating' amesabove and below the billets and inthe same direction as the after they' have traveled over the adjacentthe discharge end of 'ing' thebillets, means preheating flames forheating the preheated bi1- lets to an elevated temperature, a soakinghearth. over which the billets travel before they are discharged fromthe furnace, means for withdraw'-A ing the. products `of combustion ofthe upper flames over the billets on the soaking hearth and dischargingthem from the furnace, and means for independently withdrawing the'products of combustion of the lower flames ahead-of the soaking hearth.

30. In a continuous furnace for heating billets and the like. andthrough which the billets are caused to pass from the charging end tothe discharge end, means for introducing heating flames at the chargingend of the furnace which travel in the same direction as the billets forpreheating the same, means for introducing additional heating flamesinthe same direction as the preheating flames for heating the preheatedbillets to an elevated temperature, a soaking hearth. over which thebillets travel .before they are discharged from the furnace, means forwithdrawing the products of combustion of said flames over the billetson the soaking hearth and discharging them from the furnace, and meansresponsive to the temperature of the products vof combustion passingfrom the soaking hearth for controlling the final heated temperature ofthe billets.

31. 1n a continuous furnace-for heating muets and the like and throughwhichthe billets are caused to pass from the charging end to thedischarging end, means for introducing flames and. withdrawingtheproducts of combustion thereof adjacent the discharge end of thefurnace, and means forintroducing other flames and Withdrawingthevproducts of combustion thereof ad'- jacent the charging end of thefurnace.

. 32.' In a continuous furnace for heating billets s and the like andthrough which the billets are caused to pass from the chargingend to thedischarging end, meansfor introducing fla-mes and withdrawing theproducts of combustion .thereof adjacent the discharge end ofthefurnace, and

and the like,

means for withdrawing the products Vof combustion of said heating flamesadjacent the discharge end of the furnace.-

35. In a continuousfurnace for heating billets Athe combinationl of an'elongated chamber through which the billets pass from the charging endto the discharge end, means for introducing heating haines into thefurnace,.a flue for withdrawing the products of combustion adjacent thedischarge end of the furnace, and pyrometric means in said flueresponsive to variations in temperature in the withdrawn products afterthey have entered the'ilue and arranged to regulate said flameintroducing means.

36. In a continuous furnace for heating billets and the like, thecombination of a furnace chamber having a soaking hearth adjacent thedis; charge end over which the billets pass, means for heating saidbillets as they pass through said chamber, an outlet adjacent thedischarge end of the furnace for conducting the products' of combustionafter they have passed over the billets on the soaking hearth, heatresponsive means in 1 said outlet for controlling the heat supplied tothe furnace chamber to regulate the temperature of the billets on thesoaking hearth.

37. I n a continuous furnace for heating billets and the like, thecombination of afurnac'e chamber through which the billets pass fromthe` charging end to the discharge end and having a soaking hearthadjacent the latter end, means for heating the furnace chamber fromadjacent the charging end during normal operation, means` Y forA heatingthe billets on the soaking hearth during a cessation of the billets inthe furnace, an

outlet adjacent the discharge end of the. furnacechamber for conductingthe products of combustion after they have passed over the billets onthesoaking hearth, heat responsive means in said outlet for controllingthe heat delivered to the furnace to regulate the temperature of thebillets on the soaking hearth, and means for semeans for introducingother flames and withdrawing' a portion of the products of combustionthereof adjacent the charging end4 of the furnace and withdrawing theremainder of said products the furnace.

-33. In a continuous furnace for heating billets andthe like, thecombination of a main heating chamber, a preheating chamber connected tothe main heating chamber, a hearth extending from the charging end ofthe preheating chamber through the main heating chamber for supportforintroducing heating flames at 'the charging end of the vp reheatngchamber. andseparate means for introducing heating flames at thecharging end of the main heating chamber, and outlet means forwithdrawing the products of combustion of said heating- .charging end tothe flames adjacent to the discharge endvof the fur 3 4. In a continuousfurnace for heating billets and thelike. the combination of a mainheating chamber having a soaking hearth adjacent the discharge end, apreheating chamber connected to the other end of the main heatingchamber, a hearth extending from the `charging end of lthe preheatingchamber through the main heating ,chamber forsupporting the billets,means forinlectively transferring the application of the heat .to aselected end of the furnace when the quantity of heat delivered to thefurnace reaches a predetermined rate of ilow.

38. The method of consisting of the products of comlmstion ofsaidheating flames.

39; In a continuous furnace for heating billets and the like, thecombination vof. a furnace chamber through which the billets trave1 fromthe discharging end, burners at the charging endof. troducing heatingflames to heat the billets as they' enter thel furnaceA chamber, burnersat the discharge end of the furnace chamber for in inducing heatingnames to mak the muets before they leave the furnace chamber, an outletfor the discharge of products of combustion from the.

furnacev chamber, -and means responsive to the temperature of theproducts of combustion in said outlet for regulating said heating names.

troducing heating flames at the charging end of of the main heatingchamber and at the charge end of the main chamber, and

and separate means for outlet they enter the'furnace chamber,

40. In'al continuous furnace for heating billets and the like. thecombination of a'furnace cham ber through which the billets travel fromthe charging end tothe discharging burners at. the charging end of thefurnace chamber for introducing heating flames to heat the billets asheating billets and the like' which comprises causing heating flames totravel burners at discharge end of the furnace chamber for introducingheating flames to vsoak the billets before4 they leave the furnacechamber, and means for withdrawing products of combustion adjacent thedischarge end.

4l. In a continuous furnace for heating billets and the like, thecombination of a furnace chamber through which the billets travel fromthe charging end to thev discharge end, burners at both ends of thefurnace chamber for introducing heating ames in lines substantiallyparallel to the path ,ofl the billets, means for maintaining a flow ofnon-oxidizing gases between the heating flames and the billets, and aflue at the end of the furnace for withdrawing the nonoxidizing gasesflowing over the billets about to be discharged.

42. In a continuous furnace for heating billets and the like, thecombinationof a furnace chamber through which the billets travel fromthe charging endto the discharge end, burners at both ends of thefurnace chamber for introducing heating flames in lines substantiallyparallel to the path of the billets, means for maintaining av blanketinglayer of non-oxidizing products of combustion between the heating flamesand the billets, and a flue at the end of the furnace for withdrawingthenon-oxidizing products of combustion flowing over the billets about tobe discharged.

43. In a continuous furnace for heatingbillets and the like, thecombination of a furnace chamber through which the billets travel fromthe charging end to the discharge end, burners at both ends of thefurnace chamber'for introducing heatingilames in linessubstantiallyparallel tothe keting layer of the non-oxidizing productsof combustion, originating from the heating flames,

between the billets and the heating flames, and a flue at the end of thefurnace for withdrawing the non-oxidizing products of combustion flowingover the billets about to be discharged.

44. The method of heating billets and the like in a continuous furnace,which comprises causing heating flames to travel, in lines substantiallyparallel with the travel of the billets, from both the charging end anddischarging end of the furnace, interposing a blanket of Vnon-oxidinggases between` the billets and the flames traveling from the chargingend of the furnace, and reversing the direction of travel of theproducts of combustion ofthe flames traveling from the discharge end ofythefurnace to inter-pose a blanket of non-oxidizing gases between thebillets and said last mentioned names. v

45. The method of heating steel billets to roll-11:18temperaturewhichcomprlsestliesteell throughaheatedfurnacea,thenheatv ing'the steel from above during the nal portion of its travel throughthe furnace over a solid xefractory hearth, and heating the hearth frombelow by passing thewastegases from thefurnaceincontactwlththeundersideofthehearth.

46.Inacontinuousfurnaceforheatingbillcts and the like and through whichthe billets are caused to pass from the charging end to the dischargeend, means for introducing v heating flames at the charging end of thefurnace which., travel in the same direction as the billets for heatingthe same, a soaking hearth in the furnace over which the billets passbefore they leave the furnace, a gravity discharge slope at the'end ofthe hearth down which the billets slide as they 47. In a continuousfurnace for heating billets and the like and through which the billetsare caused to pass from the charging end to the discharge end, means forintroducing heating flames atthe charging end of the furnace whichtravel in the same direction as the billets for heating the same, heatexchange means below said furnace, a soaking hearth in the furnace overwhich the billets pass before they leave the furnace, said hearth alsoforming the top wall of the heat exchange means, and ues at thedischarge end of the furnace for withdrawing the products of combustionof said flames over the billets on the soaking hearth and directing themto the heat exchange means under the hearth.

48. In a continuous furnace for heating billets and the like and throughwhich the billets are caused to pus from the charging end to thedischarge end, means for introducing heating flames above and below thebillets at the charging end of the furnace which travel in thesamedirection as the billets for heating the same, heat exchange means belowsaid furnace having a stack flue connection, a soaking hearth in thefurnace over which the billets pass b efore theyleave the furnace, fluesat the discharge end of the furnace for withdrawing the products ofcombustion of said flames over the billets on the soaking hearth, iluesahead of the soaking hearth for independently withdrawing the productsof combustion of the flames below the billets, both of said fluesdirecting the products of combustion to said heat exchange means, anddamper means in all of said ilues for separately regulating the drafttherein.

49. 'Ihe method of operating a continuous furnace for heating billetsand the like which combillets at both ends of the furnace to provide aVgreater 'quantity of lgasesilowing over the billetsatthechargingendthanatthedischargeend sothat the surface temperature ofthe billets does not exceedthetemperatureofthebodyofthe-billetsatthetimeoftheirdischarsefromthe -furnace.

WILLIAM A. NORTON.

